Crow Hue vs JMSDF 2705 Dark Gray N4

How close are they?

ΔE 6.4, close: similar, with a visible difference side by side. JMSDF 2705 Dark Gray N4 is a little lighter, more muted than Crow Hue.

Can I use JMSDF 2705 Dark Gray N4 instead of Crow Hue?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). JMSDF 2705 Dark Gray N4 is a little lighter, more muted than Crow Hue.

Can I use Crow Hue instead of JMSDF 2705 Dark Gray N4?

The same difference applies the other way round: Crow Hue is a little darker, more saturated.

ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.